What Happened to the Switchgrass?

Or: Why is All Our Ethanol Made from Corn?
The Energy Policy Act of 2005 was signed into law by George W. Bush and created the Renewable Fuel Standard (RFS). Among other things, the RFS set goals for the amount of renewable biofuels to be blended into the nation’s petroleum fuel supply. That meant gasoline would contain ethanol and biodiesel would be blended into diesel fuel. At the time the domestic source for almost all that ethanol was corn. But corn was not supposed to be the sole source. Over time, corn was supposed to be supplanted with other sources of ethanol.

Ethanol is produced by fermenting sugars into alcohol. In the US we use corn, in other parts of the world they use sugar cane, sorghum or grain. Turns out it’s also possible to make cellulosic ethanol from sugars derived from biomass (which is a fancy name for plant trash- like stalks, leaves, etc.). It should be noted the RFS also forbid the importation of any foreign ethanol.

Another requirement of the RFS was a specified amount of ethanol must be cellulosic ethanol. Not made from corn. In 2005 there were many different biomass possibilities tossed around: crop residuals, trees, even lawn waste. The most promising of all these cellulosic solutions was switchgrass, aka Panicum Virgatum. It seemed like the perfect answer… nobody eats switchgrass, growing it produces less carbon, it takes less energy to make into fuel, and it can actually improve the soil. Yet production has failed to meet the mandated levels set out in the RFS. In fact, the targets had to be repeatedly lowered because of the dramatic shortfall in biomass-derived ethanol production.

Unfortunately, an efficient process for making biomass into ethanol at scale has been elusive. It’s much easier to suck off the sugar from corn, especially while gas has been so (relatively) inexpensive. So the Great Green Hope has fallen far short of expectations. Of course the recent price spikes at the pump might mean the equation is more appealing for fuels made from biomass.

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